ActionScript 3.0 :: How To Spawn Objects - Side / Speed And Altitude

Here is a link to what I mean: [URL]. I am spawing enemies by this right now:

public function newPlane(event:TimerEvent) {
// random side, speed and altitude
if (Math.random() > .5) {
var side:String = "left";
} else {
side = "right";
} var altitude:Number = Math.random() * 300 + 20;
var speed:Number = Math.random() * 50 + 50;
var p:Airplane = new Airplane(side,speed,altitude);
addChild(p);
airplanes.push(p);
setNextPlane();
}